Mineral fiber mat and process of making same



p 1951 T. E. PHILIPPS 2,566,960

MINERAL FIBER MAT AND PROCESS OF MAKING SAME Filed Oct. 12, 1948 r I IN VEN TOR. as o la mad, E. Pkili v u,

Patented se m, 1951 MINERAL. FIBER,.MAT AND rnoo ss OF MAKING SAME Thomas. E. Philinps, Granville, Ohio, assignor to Qwens-Gorning Eiberglas Corporation, a corporation of; Delaware Application October 12, 1948, Serial-N0. 54,116 I (Cl. HEP-1:26

8- Claims. 1

This; invention relates to the treatmentofmim. eral fibers and more particularly glass. fibers to produce a mat adapted particularly for use as a separator or retainer mat in storage batteries.

Ordinarily, in the making of mineral fiber mats of the present type, the fibers are deposited on a slowly moving conveyor to form a web or matof from a few thousandths to one quarter of. an inch in thickness. Binding material is usually applied tothe fibers either before or after being deposited on the conveyor as by spraying or dipping, and subsequently; this binding material is heated to be cured, fused or otherwise set to a form in which the fibers: are firmly bound. in the desired relation. When the mat is used as a retainer mat or separator in electric storage batteries, it is desired to have the binder resistant to the battery acids and unafiected. by the battery reactions.

Heretofore, a number of materials have been employed to bond the fibers, but these materials have. not completely satisfied the requirements where the mats are for storage battery use. The components of the binder must be resistant to acid. No component can contain chlorine since i.

the resulting formation of hydrochloric acid causes attack on the plates ofthe battery. This precludes the use of vinyl chlorides, chlorinated rubber, and the like. Also animal glues are usually leached with hydrochloric acid during their processing so that they usually contain chl'o rides and for the same reason are objectionable, nor should acetates or any organic acid derivative, acid anhydride, or other acid formingcompound be present in any of the ingredients.

In addition, practice has indicated that the presence of free nitrogen is detrimentalto the performance of a battery. Consequently; casein, albumen, and compounds which may, under some conditions, lose their nitrogen as through decomposition, cannot be used.

An object of the invention is toproduce an im: proved bonded mineral wool adapted particularly for battery use which. not only has; increased resistanceto battery acids but does not militate against the performance of the battery.

In accordance with this invention, a binder composed principally of polystyrene is employed. Polystyrene is particularly resistant to attacksu-lph-uricacid and also has excellent electrical properties and is resistant to'moisture. It; s found that the molding powder grade, that-is, medium molecular weight resin. is most desir: able, he po y ran e be n betweenfiaoto a 854100 m lecularweight. The lower molecuelarweight. resins have insufficient, strength tor; the purpo e e 3 1130 se ut en it t ese higher me ecu we ght resins. are not readily usable because of; the; den: gers and high costs incident to the use of solvents, For this reason the resin binderis. ap; p i d: in the for of an: aqueous emulsi i re s ynv The se o spersi n- 1 e att nded wi 1 great difficulty, however, in that as the vehicle-v is evaporated; during the heat treatment. of; h nde -she e in s em i ed; n. he fibetfi p a e ar c e of ha de ed: resin. wh ch ar vo an d e yen s a res t fibe s. of e me fluf n; and ether. i mere from desired compact relation where thev vehicle evaporates and; subsequent fusionv of the. binder: panticles. by the heat treatment. is incapable oi b nd ng he ibers; n o: he m-r dZ r latipn. the mat. The mats. are. asa q e ue e. or ybonded, fuzzy, and, have poor strength.

It is another object of the invention to. provide pr cess u lizin r s n i p r i ns r; b ndi g glass= fill rs n. a by which a. com act. well de nrqdu t. be obtained.

Inaccardence w th eend aspect. of 011 11: vention, the integrity of the mat is initially mainia nal by, inder unt l bse uent n th r binde Whi91linQ Ima11Y non-a hesive but is rendered; adhesive by changed; temperature conditions, replaces the preliminary binder, the final binder haying certain properties rendering it particulary useful for use in storage batteries.

The polystyrene is mixed with gelatin in a ratio of about 155 parts gelatin to parts polystyrene although other proportions ranging from about 10 parts gelatin up to 2-5 parts gelatin with "7 5 to parts of polystyrene may be used. The poly: styrene is preferably polymerized in an aqueous emulsion or dispersion so that in order to produpe the binder all that is necessary is to addjthe gelatin to the emulsion or dispersion. In some processes, the gelatin may he added to theforigi-I nal mixture to operate as the dispersing agent. in y v n the elatin adds to the stability of the suspension. v

A specific example of a binder formulation may be as follows:

12.5: lbs. polystyrene emulsion of 40% solids content and 80,690. molecular weightl bs. dibut-yl phthalate. emulsion'(28% solids content) .2 lbs. gelatin of commercial grade (chlorinefree). 47 .8 gals'of' distilled water First the dibutyl phthalate emulsion is made by adding about 13.2 lbs. of dibutyl phthalate to a solution of .5 lb. of Aerosol OT (sodium dioctyl sulfosuccinate) or other soap type dispersing agent in 33.2 lbs. of distilled water or other mineral free water with suflicient agitation to form a uniform mix. The gelatin is added to about one-half of the amount of water and the polystyrene emulsion and the dibutyl phthalate emulsion are then mixed into the gelatin solution. This is then diluted to 50 gals. by adding the remainder of the water. The agitation of the mix should only be sufficient to thoroughly combine the ingredients.

The method of applying the emulsion or mixture to the mineral fibers may be similar to any of those presently in use. The mixture may be sprayed onto the fibers as they build up into mat formation or the mat may be saturated by dipping or other suitable means. After the fibers are properly coated, the mat is heated to cause the binding agent to be converted to its final set, in the present case, to be fused. A baking temperature of 250 F. to 450 F. for three to twenty minutes, suffices to drive oif the volatiles and effect the desired fusion. The gelatin retains the fibers in place until the fusion of the polystyrene takes place and during the time the diluent is reduced to such an extent that it no longer causes the fibers to cling to each other. The styrene polymer preferably used has a lower fusion temperature as a result of its plasticization by the dibutyl phthalate but unplasticized resins may, of course, be used by resorting to higher baking temperatures. The binder of this invention makes use of the adhesiveness of gelatin in solution during the time the vehicle for the resin is being removed. The temperature of the bake is in the softening range of the styrene polymer and at this point, the resin fuses to afiord a binder for retaining the fibers together. The gelatin is apparently sufliciently incorporated in or mixed with the styrene resins, or its binding effect is not permanently required, because its leaching or attack by the battery acids has no noticeable effect on the mat.

One form of apparatus by which the present invention may be accomplished is disclosed in detail in Patent No. 2,306,347 to Games Slayter, dated December 22, 1942, but for purposes of illustration reference may be had to the accompanying drawing, in which:

Figure 1 is a schematic view of the apparatus;

Figure 2 is a view on a greatly enlarged scale of the fluid binder applied to the fibers; and

Figure 3 is a similar view illustrating the final binder stage.

Referringnow to the drawings and Figure 1 inparticular, the apparatus comprises a glass melting unit 5 of suitable construction adapted to discharge the molten glass in a plurality of fine streams. The flowing molten streams are engaged by a blast of steam or air from a blower 6 disposed adjacent the source of the streams and by which the streams are attenuated to fine fibers. The fibers are blown downwardly through the hood 8 onto a collecting surface in the form of an endless foraminous belt 9. A suction chamber I0 is provided beneath the belt 9 to aid in collecting the fibers in the form of a mat I I in which the fibers are haphazardly arranged The thickness of the mat is primarily controlled by regulating the speed of the belt 9. Thus, increasing the conveyor speed produces a thinner mat and conversely, slowing the conveyor provides for a greater thickness of mat.

As the mat is carried from beneath the hood 8 on the conveyor 9, it is drafted into a sheet [2 by mechanism including a draft bar or idler roller l4 and drafting rolls l5 and IS. The sheet [2 passes downwardly from the roll l4 and around the roll l5 which is driven by any suitable mechanism. The roll l6 cooperates with the roll I5 as a pinch roll to assure uniform contact of the sheet with the roll [5. The rolls l5 and I6 serve a two-fold purpose since the roll [5 is mounted within a container I 1 and is adapted for rotation partially submerged in a binder solution l8. Thus the sheet I2 is saturated with binder as it is drawn from the conveyor 9 and excess binder is squeezed out as the sheet passes between the rolls l5 and 16.

The binder impregnated sheet as it leaves the dipping tank passes through a drying and/or curing oven 20 in which a suitable baking tem' perature is maintained preferably by circulating heated air. The sheet is supported in the oven 20 on a traveling conveyor belt 2! and has a tensioning roll 22 cooperating therewith. The roll 22 and conveyor 2| have similar surface speeds which are slightly in excess of the drafting speed of the roll [5. This difierence in speed may be only sufi'icient to prevent the sheet from wrinkling as the binder is cured. The cured sheet upon leaving the oven 29 may be rolled as at 24 or cut into sheets for storage or subsequent handling and fabrication.

Figure 2 illustrates on a gigantic scale several fibers F which represent the primary binder phase, that is, the mat after passing through the binder solution but before sufiicient heat has been applied to cause the resin to flow. Passage of the mat through the binder I8 in the tank 11 produces a film on the fibers as indicated at 28. This film 0r residuary emulsion completely wets and covers the fibers with a uniform coating embodying the solubilized gelatin. Solid particles of resin dispersed in the gelatin emulsion and indicated at 29, are adhered to the fiber surface by the fluid phase of the binder as the volatiles evaporate. The preliminary heating of the binder causes the liquid to evaporate thereby leaving a relatively solid bond of gelatin holding the fibers together. Thus fiufliness in the mat and separation of fibers is prevented until the permanent resin bond is accomplished by additionally heating the mat.

The solids content in the above stated amount have been found suflicient when melted to form a substantially uniform film on the fiber as indicated at 30 in Figure 3. subjecting the mat to the baking temperature produces a transition from the showing in Figure 2 to that of Figure 3 whereby the heat plasticized resin fiows about the fibers and their points of contact and forms a permanent bond.

It is to be understood that modifications and variations may be eifected Within the spirit of the present invention as defined by the appended claims.

I claim:

1. In the method of manufacturing a bonded mat of glass fibers, the steps of treating the glass fibers with a composition comprising discrete particles of polystyrene which are of the molding powder grade and dispersed in an aqueous solution of gelatin, volatilizing the water to deposit the discrete particles of polystyrene on the glass fiber surfaces while the gelatin functions aseaeoo throughout as a temporary binder to hold the fibers in predetermined form, and then heating to fuse the discrete particles for conversion thereof into an adhesive film.

2. In the method of manufacturing battery mats of bonded glass fibers, the steps of coating the glass fibers with a composition comprisin discrete particles of polystyrene, said particles having a medium molecular weight suitable for molding and being dispersed in an aqueous solution of gelatin, the materials being present in the ratio of 75 to 90 parts by weight of discrete particles to to 25 parts by weight of gelatin, and evaporating the water to deposit the discrete particles on the glass fiber surfaces while the gelatin functions as a binder to hold the glass fibers in predetermined mat formation, and then heating the mass to a temperature of 250 to 400 F. to fuse the discrete particles and develop their adhesive characteristics.

3. In the method of manufacturing a glass fiber battery mat, the steps of treating glass fibers with a composition comprising discrete particles of polystyrene having a polymeric growth suitable for molding dispersed in an aqueous solution of gelatin, removing the water by heat to deposit the polystyrene on the glass fiber surfaces while the gelatin functions as an intermediate adhesive to hold the fibers in mat form, and then heating to fuse the discrete particles of polystyrene to form adhesive films.

4. In the method of manufacturing a battery mat of glass fibers, the steps of coating glass fibers with a composition comprising discrete particles of polystyrene having a molecular weight between 65,000 and 85,000 and dispersed in an aqueous solution of gelatin, the materials bein present in the ratio of '75 to 90 parts polystyrene to 10 to 25 parts gelatin, heating the mass to remove the water while the gelatin functions as an intermediate adhesive to hold the fibers in mat form, and then heating to fuse the discrete particles of polystyrene to develop their adhesive characteristics.

5. In the method of manufacturing a battery mat of glass fibers; the steps of coating glass fibers with a composition comprising discrete particles of polystyrene having a molecular weight between 65,000 and 85,000 and dispersed in an aqueous solution of gelatin, the materials being present in the ratio of to parts polystyrene to 10 to 25 parts gelatin, heating the mass to remove the water while the gelatin functions as an intermediate adhesive to hold the fibers in mat form, and then heating the mass to a temperature of 250 to 400 F. to convert the discrete particles of polystyrene to adhesive films.

6. As an article of manufacture, a mineral fibrous mat product carrying a substantially uniform continuous film on the surface of the individual fibers, said film including a binder composition consisting essentially of fused polystyrene having incorporated therein a substantial amount of gelatin.

7. As an article of manufacture, a mineral fibrous mat product carrying a substantially uniform continuous film on the surface of the individual fibers, said film including a binder com position consisting essentially of fused polystyrene having incorporated therein a substantial amount of gelatin, said polystyrene having a molecular weight between 65,000 and 85,000.

8. As an article of manufacture, a mineral fibrous mat product carrying a substantially uniform continuous film on the surface of the individual fibers, said film including a binder com position consisting essentially of 75 to 90 parts by weight of fused polystyrene and 10 to 25 parts by weight of gelatin.

THOMAS E. PHILIPPS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,230,271 Simpson Feb. 4, 1941 2,306,347 Slayter Dec. 22, 1942 2,311,613 Slayter Feb. 16, 19-43 2,477,407 Grant et al July 26, 1949 

1. IN THE METHOD OF MANUFACTURING A BONDED MAT OF GLASS FIBERS, THE STEPS OF TREATING THE GLASS FIBERS WITH A COMPOSITION COMPRISING DISCRETE PARTICLES OF POLYSTYRENE WHICH ARE OF THE MOLDING POWDER GRADE AND DISPERSED IN AN AQUEOUS SOLUTION OF GELATIN, VOLATILIZING THE WATER TO DEPOSIT THE DISCRETE PARTICLES OF POLYSTYRENE ON THE GLASS FIBER SURFACES WHILE THE GELATIN FUNCTIONS THROUGHOUT AS A TEMPORARY BINDER TO HOLD THE FIBERS IN PREDETERMINED FORM, AND THEN HEATING TO FUSE THE DISCRETE PARTICLES FOR CONVERSION THEREOF INTO AN ADHESIVE FILM. 